JP2008167198A - Noise canceling circuit and electronic circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently detect unnecessary radiation generated from a digital signal processing circuit part. <P>SOLUTION: The unnecessary radiation generated from a baseband processing circuit part 5 mounted at a prescribed position on a substrate is detected by a coil part 7 comprised of wiring in the prescribed shape formed at a neighborhood position of the baseband processing circuit part 5 and a signal for canceling the unnecessary radiation detected by the coil part 7 is generated by a cancellation signal generation part 39. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a noise cancellation circuit and an electronic circuit.

  A phenomenon called “crosstalk” in which signals of other lines are superimposed on a certain line is known, and crosstalk is a typical example. Since crosstalk is a major factor in signal degradation, various techniques have been devised for preventing crosstalk or for eliminating mixed crosstalk components.

As an example, Patent Document 1 discloses a technique for generating a signal for canceling mixed crosstalk components (hereinafter referred to as “cancellation signal”) and removing the crosstalk components.
U.S. Pat. No. 7,050,388

  By the way, in a module in which a digital signal processing circuit unit and an analog signal processing circuit unit are mounted on a substrate, the characteristics of the analog signal processing circuit unit deteriorate due to high-frequency noise called unnecessary radiation generated from the digital signal processing circuit unit. There is a case. In this case, there is a method of applying a technique disclosed in Patent Document 1 to generate a cancel signal for canceling unnecessary radiation generated from the digital signal processing circuit unit, and adding it to the signal of the processing system of the analog signal processing circuit unit. Although it is conceivable, there is a problem of how to detect unnecessary radiation efficiently.

  Also, a method of reducing the influence of unnecessary radiation by the digital signal processing circuit unit by mounting the analog signal processing circuit unit at a sufficient distance from the digital signal processing circuit unit can be considered. The size will increase.

  The present invention has been made in view of the above-described problems.

  A first invention for solving the above problems is a wiring having a predetermined shape formed at a position close to a digital signal processing circuit portion mounted at a predetermined position on a substrate, and is generated from the digital signal processing circuit portion. It is a noise cancellation circuit including a coil unit that detects unnecessary radiation and a cancel signal generation unit that generates a signal for canceling unnecessary radiation detected by the coil unit.

  According to the first aspect of the present invention, the unnecessary radiation generated from the digital signal processing circuit unit mounted at a predetermined position on the substrate is a coil unit formed of a predetermined shape of wiring formed in the vicinity of the digital signal processing circuit unit. A signal for canceling the detected unnecessary radiation is generated by the cancel signal generation unit.

  For example, by forming the coil portion on the substrate immediately below the digital signal processing circuit portion, unnecessary radiation generated from the digital signal processing circuit portion can be efficiently detected. Also, with this configuration, it becomes possible to mount other electronic circuits such as an analog signal processing circuit unit in the vicinity of the digital signal processing circuit unit, so that an increase in the overall size of the module can be prevented, and circuit arrangement design can be prevented. The degree of freedom is improved.

  As a second invention, a noise cancellation circuit in which the coil section in the noise cancellation circuit of the first invention is formed below the digital signal processing circuit section may be configured.

  According to the second aspect of the invention, the unwanted radiation generated from the digital signal processing circuit unit is detected by the coil unit formed below the digital signal processing circuit unit.

  As a third invention, a noise cancellation circuit in which the coil part in the noise cancellation circuit of the second invention is formed below a predetermined circuit part constituting the digital signal processing circuit part may be configured.

  According to the third aspect of the invention, the unwanted radiation generated from the predetermined circuit unit of the digital signal processing circuit unit is detected by the coil unit formed below the predetermined circuit unit.

  As a fourth invention, a noise cancellation circuit in which the coil section in the noise cancellation circuit of the second invention is formed below a memory circuit section constituting the digital signal processing circuit section may be configured.

  According to the fourth aspect of the invention, unnecessary radiation generated from the memory circuit portion of the digital signal processing circuit portion is detected by the coil portion formed below the memory circuit portion.

  As a fifth invention, a noise cancellation circuit in which the coil portion in the noise cancellation circuit of the first invention is formed along the outer periphery of the digital signal processing circuit portion may be configured.

  According to the fifth aspect of the invention, the unwanted radiation generated from the digital signal processing circuit unit is detected by the coil unit formed along the outer periphery of the digital signal processing circuit unit.

  Further, as a sixth invention, an electronic circuit including the noise cancellation circuit of any one of the first to fifth inventions and the digital signal processing circuit unit may be configured.

  As a seventh invention, an electronic circuit in which the digital signal processing circuit section in the electronic circuit of the sixth invention is flip-chip mounted above the coil section may be configured.

  According to the seventh aspect, since the coil section faces the circuit surface of the digital signal processing circuit section, it becomes possible to efficiently detect unnecessary radiation generated from the digital signal processing circuit section.

  As an eighth invention, the digital signal processing circuit section in the electronic circuit of the sixth or seventh invention may constitute an electronic circuit which is a GPS satellite signal processing circuit section.

  According to the eighth invention, in combination with the above-described invention, a signal for canceling unnecessary radiation generated from the processing circuit unit for GPS satellite signals is generated.

  Hereinafter, an embodiment in which the present invention is applied to a GPS (Global Positioning System) module will be described with reference to the drawings. However, embodiments to which the present invention is applicable are not limited to this.

1. Configuration FIG. 1 is a block diagram showing a functional configuration of a GPS module 1 in the present embodiment. The GPS module 1 includes an RF (Radio Frequency) receiving circuit unit 3, a baseband processing circuit unit 5, and a coil unit 7.

  The coil unit 7 and the cancellation signal generation unit 39 included in the RF reception circuit unit 3 constitute a noise cancellation circuit 10 that is a characteristic configuration of the present embodiment. Further, the RF receiving circuit unit 3 and the baseband processing circuit unit 5 can be manufactured as separate LSIs (Large Scale Integration) or as a single chip.

  The RF reception circuit unit 3 includes an addition unit 31, a SAW (Surface Acoustic Wave) filter 33, an LNA (Low Noise Amplifier) 35, an RF conversion circuit unit 37, and a cancel signal generation unit 39. An RF signal receiving circuit.

  The adder 31 is an adder that adds the cancel signal generated by the cancel signal generator 39 to an RF signal including a GPS satellite signal as a radio signal received by the GPS antenna 2. Output to the filter 33.

  The SAW filter 33 is a bandpass filter that passes a predetermined frequency band component of the signal output from the adder 31, and outputs the passed signal to the LNA 35.

  The LNA 35 is a low noise amplifier that amplifies the signal that has passed through the SAW filter 33, and outputs the amplified signal to the RF conversion circuit unit 37.

  The RF conversion circuit unit 37 multiplies the signal amplified by the LNA 35 by a predetermined oscillation signal, thereby down-converting the RF signal into an intermediate frequency signal (hereinafter referred to as “IF (Intermediate Frequency) signal”), After the IF signal is amplified, it is converted into a digital signal by an A / D converter and output to the baseband processing circuit unit 5.

  The cancel signal generation unit 39 is a circuit unit that generates a signal for canceling unnecessary radiation generated from the baseband processing circuit unit 5 detected by the coil unit 7 (hereinafter referred to as “cancel signal”). A cancel signal is output to the adder 31. The cancel signal generation unit 39 includes, for example, a phase shift unit that shifts the phase of unwanted radiation input from the coil unit 7 by 180 degrees, an attenuation unit that attenuates the signal phase-shifted by the phase shift unit with a predetermined attenuation rate, and It is configured with.

  In the GPS module 1, the RF receiving circuit unit 3 and the baseband processing circuit unit 5 are arranged at positions close to each other, so that unnecessary radiation generated from the baseband processing circuit unit 5 is generated from the GPS antenna 2 to the RF receiving circuit unit. 3 is superimposed as noise on the signal output to 3. However, since the signal output from the GPS antenna 2 is added to the cancel signal generated by the cancel signal generator 39 in the adder 31, noise caused by the superimposed unnecessary radiation is cancelled.

  The baseband processing circuit unit 5 performs correlation processing on the IF signal output from the RF receiving circuit unit 3 to capture and extract GPS satellite signals, decodes the data, and extracts navigation messages, time information, etc. This is a circuit unit that performs pseudorange calculation, positioning calculation, and the like. The GPS satellite signal is a spread spectrum modulated signal called C / A code (Coarse and Acquisition).

  The baseband processing circuit unit 5 includes a circuit for performing correlation processing, a circuit for generating a spreading code (code replica) for performing correlation calculation, a circuit for decoding data, and a baseband processing circuit unit 5 to an RF receiving circuit unit 3 is provided with a central processing unit (CPU) 51 that is a processor that performs various arithmetic processes by comprehensively controlling each unit of 3, and a read only memory (ROM) 53 and a random access memory (RAM) 55 that are memory circuit units. Configured.

  The coil unit 7 is a wiring having a predetermined shape formed in the vicinity of the baseband processing circuit unit 5. The coil unit 7 detects unnecessary radiation generated from the baseband processing circuit unit 5 and outputs it to the cancel signal generation unit 39.

FIG. 2 is a view for explaining the form of the coil section 7.
Each circuit unit constituting the baseband processing circuit unit 5 generates unnecessary radiation along with the circuit operation. Among them, the circuit unit that generates unnecessary radiation having a particularly high signal level is the RAM 55. Therefore, in the present embodiment, unnecessary radiation generated mainly from the RAM 55 is detected by forming the coil portion 7 on the substrate below the RAM 55.

  The coil portion 7 is formed of a spiral coil wiring called a spiral inductor, and the size thereof is approximately the same as that of the RAM 55. Further, although the line width and the line-to-line distance of the spiral inductor are design matters, the number of turns is preferably “3” or more in order to effectively detect unnecessary radiation.

  FIG. 3 is a longitudinal sectional view of the RAM 55 portion of the baseband processing circuit unit 5. However, the substrate 100 is not hatched because a plurality of layers such as a wiring layer are formed therein.

  On the upper surface of the substrate 100, a spiral inductor 101 as the coil portion 7 is formed by substrate wiring. From above, a chip (hereinafter referred to as “BBIC (Base Band Integrated Circuit)”) 105 of the baseband processing circuit unit 5 is bonded and mounted by the adhesive layer 103 with the circuit surface 105a facing up. Has been.

  A terminal electrode 107 is formed on the circuit surface 105a of the BBIC 105, and is connected to a substrate electrode 109 formed on the substrate 100 by a bonding wire 111 made of a metal such as Al, Cu, or Au. This BBIC 105 mounting method is a face-up mounting method known as wire bonding mounting.

  As the adhesive layer 103 that adheres the substrate 100 and the BBIC 105, for example, an adhesive such as an epoxy resin can be used. However, if the magnetic permeability of the adhesive layer 103 is low, the spiral inductor 101 cannot detect unnecessary radiation generated from the BBIC 105. Therefore, the magnetic permeability of the adhesive layer 103 is increased by diffusing magnetic powder such as ferrite. It is good to improve.

2. According to the present embodiment, unnecessary radiation generated from the baseband processing circuit unit 5 mounted at a predetermined position on the substrate 100 is caused by the wiring having a predetermined shape formed in the vicinity of the baseband processing circuit unit 5. A signal that is detected by the coil unit 7 and cancels unnecessary radiation detected by the coil unit 7 is generated by the cancel signal generation unit 39.

  Since the coil unit 7 is formed below the RAM 55 which is a memory circuit unit constituting the baseband processing circuit unit 5, it is possible to efficiently detect unnecessary radiation having a high signal level mainly generated from the RAM 55. . Moreover, since the noise of the unnecessary radiation superimposed on the signal received by the GPS antenna 2 is canceled by the noise cancellation signal generated by the cancellation signal generation unit 39, the RF reception circuit unit 3 and the baseband processing circuit unit 5 There is no restriction on the distance between the arrangements, and it is possible to mount them at positions close to each other, which can contribute to the reduction of the module size and the improvement of the degree of freedom of the circuit arrangement design.

3. Other Examples 3-1. Digital Signal Processing Circuit Unit The present invention can be applied to any circuit unit as long as it is a circuit unit that performs digital signal processing in addition to the baseband processing circuit unit 5. In other words, any digital signal processing circuit unit that generates unnecessary radiation with circuit operation can be applied.

3-2. Mounting Method In the above-described embodiment, the wire bonding mounting is described as an example of the mounting method of the BBIC 105, but the mounting method is not limited to this.

  FIG. 4 is a longitudinal sectional view of the RAM 55 portion when the BBIC 105 is flip-chip mounted. Flip chip mounting is a face-down mounting method in which mounting is performed with the circuit surface of the chip facing the substrate.

  On the substrate 100, the spiral inductor 101 is formed by substrate wiring, as in FIG. On the terminal electrode 107 of the BBIC 105, a bump electrode called a bump 108 made of a metal such as Au or Pb is formed. The circuit surface 105a is formed on the lower surface so that the bump 108 contacts the substrate electrode 109. In the state, the BBIC 105 is mounted on the substrate 100.

  A gap between the substrate 100 and the BBIC 105 is filled and cured with a resin adhesive called an underfill 113. However, in this case as well, in order to enable detection of unnecessary radiation by the spiral inductor 101, it is preferable to improve the magnetic permeability of the underfill 113 by including magnetic powder.

  In flip-chip mounting, the spiral inductor 101 faces the circuit surface 105a of the BBIC 105, so that unnecessary radiation generated from the BBIC 105 can be detected more efficiently than in wire bonding mounting.

3-3. Shape of Coil Part In the embodiment described above, the shape of the coil part 7 has been described as being spiral, but other shapes are also possible. For example, as shown in FIG. 5, a zigzag coil wiring called a meander inductor may be formed on a substrate immediately below the RAM 55. The meander inductor line width and line-to-line distance are design matters, but in order to effectively detect unwanted radiation, the number of parallel lines (line) is more preferably “3” or more.

  Further, a coil wiring may be formed along the outer periphery of the baseband processing circuit unit 5. For example, in FIG. 6, a U-shaped coil wiring is formed on the substrate along the outer periphery of the RAM 55. In this way, unnecessary radiation can be detected simply by turning the wiring around the generation source of unnecessary radiation.

3-4. Position / Size of Coil Part The coil part 7 may be formed below the CPU 51 and the ROM 53 instead of below the RAM 55, or may be formed below the CPU 51 and the ROM 53 in addition to the RAM 55. Each coil part may be connected in parallel. Further, as shown in FIG. 7, the coil portion 7 may be formed so as to cover the entire baseband processing circuit portion 5. In this case, not only unnecessary radiation generated from the RAM 55 but also unnecessary radiation generated from the CPU 51 and the ROM 53 can be efficiently detected.

  Further, the coil unit 7 may be laminated and formed inside the substrate 100 instead of being laminated on the substrate 100.

3-5. Noise Canceling Circuit In the above-described embodiment, the cancel signal generating unit 39 of the noise canceling circuit 10 has been described as being incorporated in the RF receiving circuit unit 3, but the canceling signal generating unit 39 is independent of the RF receiving circuit unit 3. The noise canceling circuit 10 may be provided independently as a circuit unit.

The block diagram which shows the structure of a GPS module. The figure for demonstrating the form of a coil part. The longitudinal cross-sectional view of RAM part. The longitudinal cross-sectional view of the RAM part in a modification. The figure for demonstrating the form of the coil part in a modification. The figure for demonstrating the form of the coil part in a modification. The figure for demonstrating the form of the coil part in a modification.

Explanation of symbols

1 GPS module, 2 GPS antenna, 3 RF receiving circuit section,
5 Baseband processing circuit section, 7 Coil section, 10 Noise cancellation circuit,
31 adder, 33 SAW filter, 35 LNA, 37 RF conversion circuit,
39 Cancel signal generator, 51 CPU, 53 ROM, 55 RAM,
100 substrate, 101 spiral inductor, 103 adhesive layer,
105 BBIC, 107 terminal electrode, 109 substrate electrode,
111 Bonding wire

Claims (8)

A coil part for detecting unnecessary radiation generated from the digital signal processing circuit unit, comprising a wiring having a predetermined shape formed at a position close to the digital signal processing circuit unit mounted at a predetermined position on the substrate;
A cancel signal generating unit that generates a signal for canceling unnecessary radiation detected by the coil unit;
Noise cancellation circuit with   The noise cancellation circuit according to claim 1, wherein the coil unit is formed below the digital signal processing circuit unit.   The noise cancellation circuit according to claim 2, wherein the coil section is formed below a predetermined circuit section constituting the digital signal processing circuit section.   The noise cancellation circuit according to claim 2, wherein the coil section is formed below a memory circuit section constituting the digital signal processing circuit section.   The noise cancellation circuit according to claim 1, wherein the coil portion is formed along an outer periphery of the digital signal processing circuit portion.   An electronic circuit comprising the noise cancellation circuit according to any one of claims 1 to 5 and the digital signal processing circuit unit.   The electronic circuit according to claim 6, wherein the digital signal processing circuit unit is flip-chip mounted above the coil unit.   The electronic circuit according to claim 6, wherein the digital signal processing circuit unit is a GPS satellite signal processing circuit unit.

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